1. Field of the Invention
The present invention relates to a color electrophotographic image forming apparatus which employs a rotary type development process.
2. Description of the Related Art
A conventional full color image forming apparatus has been widespreadly known, which includes one image bearing member and a rotatable supporting member that integrally supports a plurality of development devices. The image forming apparatus like this employs a development process for developing an electrostatic latent image that has been formed on the surface of an image bearing member by sequentially changing a development device at a predetermined timing. The image forming apparatus which uses the rotatable development device supporting member (rotary) like this, which integrally supports a plurality of development devices and which is configured to develop an electrostatic latent image formed on the surface of one image bearing member by sequentially changing the development device, is referred to as a “rotary type image forming apparatus”.
Japanese Patent Application Laid-Open No. 2005-148319 discusses a configuration of the conventional rotary type image forming apparatus. Generally, in the rotary type development process, it is necessary, for each development device provided to each color developer, to execute an operation, at a development position, for sequentially causing a developer bearing member of each development device to abut on and separate from the surface of the image bearing member. The development device is changed by rotating the development device supporting member while the development device is separated from the surface of the image bearing member.
In the conventional image forming apparatus, the operation for causing the developer bearing member to abut on and separate from the surface of the image bearing member is executed by moving the development device supporting member in the direction of the diameter of the image bearing member (in the direction of the rotational axis) by a cam having a driving force. However, the following problem may arise in the above-described conventional rotary type image forming apparatus.
Specifically, in the conventional image forming apparatus, because the image forming apparatus executes the operation for causing the developer bearing member to abut on and separate from the surface of the image bearing member by moving the development device supporting member in the direction of the diameter of the image bearing member, it becomes necessary to provide a space for moving the development device supporting member. In addition, in the above-described conventional image forming apparatus, it becomes necessary to provide a cam as a drive unit for moving the development device supporting member in the direction of the diameter of the image bearing member during the operation for causing development device supporting member abut on or separate from the surface of the image bearing member.
To paraphrase this, in the conventional rotary type image forming apparatus, it becomes necessary to provide a space and a drive unit for causing the developer bearing member to abut on and separate from the surface of the image bearing member by moving the entire development device supporting member in the direction of diameter of the image bearing member. Accordingly, it becomes difficult neither to reduce the size of the apparatus body nor to reduce the cost.
For example, the above-described problem may be solved by the following configuration. Specifically, the operation for causing the developer bearing member to abut on and separate from the surface of the image bearing member may be executed by directly utilizing the rotation of the development device supporting member instead of using a drive unit, such as a cam.
However, if the operation for causing the developer bearing member to abut on and separate from the surface of the image bearing member by directly utilizing the rotation of the development device supporting member, the developer applied to the surface of the developer bearing member may adhere to the surface of the image bearing member in a streak-like shape during the abutment and the separation operation. As a result, image defect may arise.